1. Field of the Invention
The present invention relates to a personal data assistant terminal with radio which has data transmission and reception functions by a radio wave and a plurality of different power supply modes and includes a central processing unit (CPU) which effects power supply control.
2. Description of the Related Art
A conventional personal data assistant terminal with radio includes a CPU which often has a function of controlling power supply thereto to control the terminal.
In a personal data assistant terminal with radio of the type described, transition of the power supply condition is performed such that, if it is assumed, for example, that the three power supply conditions of xe2x80x9cFULLxe2x80x9d, xe2x80x9cSLOWxe2x80x9d and xe2x80x9cSUSPENDxe2x80x9d are available, then although the applied power supply condition can be changed over from the xe2x80x9cFULLxe2x80x9d condition to the xe2x80x9cSLOWxe2x80x9d condition or to the xe2x80x9cSUSPENDxe2x80x9d condition arbitrarily depending upon a set state of a register of the CPU, it can be changed over from the xe2x80x9cSLOWxe2x80x9d condition only to the xe2x80x9cSUSPENDxe2x80x9d condition depending upon the set state of the register, or transition to the xe2x80x9cFULLxe2x80x9d condition is allowed only when some interruption occurs. Further, when it is tried to render the terminal operative while the power supply is in the xe2x80x9cSUSPENDxe2x80x9d condition, the applied power supply condition can be changed over only to the xe2x80x9cFULLxe2x80x9d condition.
Meanwhile, in a terminal which utilizes a radio wave, operation noise of a CPU has a bad influence on a radio signal transmitted from or received by the terminal. Therefore, in order to reduce such noise, the terminal requires such a countermeasure as to make the frequency of an operation clock signal of the CPU as low as possible upon transmission or reception of a radio signal.
However, if it is intended to render the terminal operative while the power supply is in the xe2x80x9cSUSPENDxe2x80x9d condition, since such a conventional power supply control method as described above changes over the applied power supply condition only to the xe2x80x9cFULLxe2x80x9d condition, the terminal is influenced much by noise then.
Meanwhile, an automatic terminating system for a small-size portable terminal which effects power supply control in response to termination of a call to a modem of a handy terminal which includes a modem phone and an interface unit is disclosed in Japanese Patent Laid-Open Application No. Heisei 2-209069. In the automatic terminating system, the power supply control is effected using two CPUs, that is, a main CPU and a sub CPU, and power supply to the main CPU is controlled between on and off by power supply control of the sub CPU, and the sub CPU detects a carrier indicator (CI) signal of the modem by hardware and changes over the mode of itself from a sleep mode to an on mode. In this manner, each of the CPUs has the only two modes of the power supply on mode and the power supply off mode.
A portable terminal which makes use of an IC card is disclosed in Japanese Patent Laid-Open Application No. Heisei 6-150076. In the portable terminal, the IC card discriminates a command issued from a host CPU, and a CPU in the IC card issues a command to the IC card to put the terminal and the IC card into individual power supply modes.
However, where a CPU itself issues a command of software to enter power supply modes as in the portable terminal which makes use of an IC card described above, if the CPU has a plurality of interrupt inputs, then the CPU must discriminate the type of the current interruption and issue a command for a corresponding power supply mode so as to enter the pertaining power supply mode. Therefore, such a procedure that the applied power supply mode is changed over to a power saving mode after the xe2x80x9cFULLxe2x80x9d operation mode is entered once must be taken. Such a power supply transition condition is schematically illustrated in FIG. 8. This is because an apparatus which makes use of a radio wave suffers from the problem that, if the xe2x80x9cFULLxe2x80x9d operation mode is entered once, then the radio wave condition is deteriorated to such a degree as to disable radio wave communication by electromagnetic noise generated from the CPU. Since noise generated from the CPU decreases in proportion to the square of the distance between the CPU and the radio unit, the distance between the radio unit and the CPU should be maximized. However, an apparatus having a small-size housing such as a portable terminal basically suffers from the problem described above since a sufficient distance cannot be secured between the radio unit and the CPU.
Meanwhile, in the automatic terminating system for a small-size portable terminal disclosed in Japanese Patent Laid-Open Application No. Heisei 2-209069 mentioned above, the CPU has only two power supply modes of the power supply on mode and the power supply off mode. Where only the two power supply on and off modes are involved, the main CPU is put into an operative condition by an external factor only when the xe2x80x9cFULLxe2x80x9d mode is entered. Consequently, it is impossible to control the speed of the CPU in order to minimize the influence upon a radio wave upon operation of the CPU as in a personal data assistant terminal with radio. Accordingly, it is difficult to handle radio data while the CPU is operative.
It is an object of the present invention to provide a personal data assistant terminal with radio wherein a power supply mode required by a peripheral circuit to a CPU can be entered arbitrarily.
In order to attain the object described above, according to an aspect of the present invention, there is provided a personal data assistant terminal with radio which has data transmission and reception functions by a radio wave and a plurality of different power supply modes, comprising a CPU for effecting power supply control of the personal data assistant terminal with radio, the CPU having a terminal for receiving, as an input signal thereto, a power supply mode change-over signal representative of a power supply mode which is to be entered subsequently by the CPU, and another terminal for receiving, as an input signal thereto, a power supply mode defining signal for defining a power supply mode represented by the power supply change-over signal.
The power supply modes may include a xe2x80x9cFULLxe2x80x9d mode in which a system clock signal with which the CPU operates has a first frequency, a xe2x80x9cSLOWxe2x80x9d mode in which the system clock signal has a second frequency lower than the first frequency, a xe2x80x9cDOZE mode in which the system clock signal has a third frequency lower than the second frequency and some of functions of the CPU are inoperative, and a xe2x80x9cSUSPENDxe2x80x9d mode in which the power supply is close to that in a power supply off mode in which no power is supplied to the CPU.
The personal data assistant terminal with radio may further comprise an external peripheral circuit which includes means for indicating a power supply mode to be entered subsequently to the CPU, the power supply mode defining signal being put into an effective condition in a timed relationship with a power supply transition timing signal of the peripheral circuit.
Preferably, the CPU is started in a mode in which the CPU generates minimum electromagnetic noise in response to an instruction from a circuit which controls power supply to a peripheral circuit in response to a starting instruction of the CPU.
In the personal data assistant terminal with radio, a mode to which the applied power supply mode is to be changed over subsequently when the CPU is to return to an operative condition from the xe2x80x9cSUSPENDxe2x80x9d mode thereof can be determined using the external input signals, and consequently, transition to an arbitrary power supply mode requested by the external peripheral circuit to the CPU can be performed. Consequently, for example, from the xe2x80x9cSUSPENDxe2x80x9d mode of the CPU in which the CPU is almost in a stopping condition, the CPU can be put into an operative condition in the xe2x80x9cSLOWxe2x80x9d mode or the xe2x80x9cDOZExe2x80x9d mode in which the CPU generates comparatively little noise in accordance with a request from the external peripheral circuit such as a radio communication circuit of the personal data assistant terminal with radio. Accordingly, noise generation by the CPU to the radio communication circuit can be suppressed to the utmost.
Basically, by the construction described above, also in such a case that the CPU is put into an operative condition from the xe2x80x9cSUSPENDxe2x80x9d mode in response to a trigger provided by inputting of data of a radio wave, transition not only to the xe2x80x9cFULLxe2x80x9d mode but also to the xe2x80x9cSLOWxe2x80x9d mode can be performed by setting the mode to be entered subsequently through the external input terminals.
This signifies that, particularly when power supply control is to be performed in a peripheral circuit which includes a sub CPU or a like element, the power supply to the CPU can be controlled directly from the outside of the CPU.
In summary, with the personal data assistant terminal with radio, since the applied power supply mode of the CPU can be changed over arbitrarily using a signal of a peripheral circuit to the CPU, it is possible to put the personal data assistant terminal with radio from a xe2x80x9cSUSPENDxe2x80x9d condition to a power supply on condition while a radio section of the personal data assistant terminal with radio remains operative and particularly to put the CPU into an operative condition in the xe2x80x9cSLOWxe2x80x9d mode in which noise generation of the CPU is comparatively little so that the radio section may not be stopped from communication by electromagnetic noise of the CPU. Consequently, the personal data assistant terminal with radio is less liable to be influenced by electromagnetic noise of the CPU during radio communication.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference symbols.